ESTRO 2022 - Abstract Book

S723

Abstract book

ESTRO 2022

patients.

Materials and Methods The validation cohort consisted of 1,520 BC patients from 3 other centres treated with adjuvant radiotherapy in the same period. After application of both models to the patients included in the validation cohort, model performance was assessed by discrimination in terms of a c-statistic and calibration in terms of calibration plots and the observed/expected ratio. If needed, models were updated. Results Mean follow up was 7.6 years and the cumulative ACE incidence at 10 years was 1.7% for the validation cohort. This cumulative ACE incidence at 10 years was significantly lower than observed in the development set (4.8%). Model performance after external validation was similar for both models (table 2). External validation showed good discrimination: c-statistic 0.72 (0.61-0.83) and 0.71 (0.60-0.82) for model 1 and 2, respectively. There was an overestimation of the ACE risk by a factor 2 in the validation cohort. But after recalibration (adjustment of the mean linear predictor and baseline risk, but same coefficients) the prediction models performed well in the validation cohort.

Conclusion We externally validated two models based on different cardiac DVH parameters for ACE risk in the first 10 years after radiotherapy. We prefer the model including whole heart Dmean and left ventricle V5 as these DVH-parameters are more suitable to apply in dose optimization strategies.

MO-0804 Determinants of fatigue and longitudinal changes up to 2 years post-radiotherapy for breast cancer

C. Rosas 1,2 , T. Rattay 3 , D. Azria 4 , R.M. Elliott 5 , S. Gutiérrez-Enríquez 6 , T. Rancati 7 , B.S. Rosenstein 8 , D. De Ruysscher 9 , E. Sperk 10 , H. Stobart 11 , R.P. Symonds 3 , C.J. Talbot 3 , M.C. De Santis 12 , A. Vega 13 , L. Veldeman 14 , A. Webb 15 , C.M. West 5 , J. Chang-Claude 1,16 , P. Seibold 1 1 German Cancer Research Center (DKFZ), Division of Cancer Epidemiology, Heidelberg , Germany; 2 Ludwig-Maximilians- Universität München (LMU), IBE , Munich , Germany; 3 University of Leicester, Leicester Cancer Research Centre, Leicester , United Kingdom; 4 ICM Institut du Cancer Montpellier, Department of Radiation Oncology, Montpellier, France; 5 The University of Manchester, Division of Cancer Sciences, Manchester , United Kingdom; 6 Vall d'Hebron Institute of Oncology (VHIO), Oncogenetics Group, Barcelona , Spain; 7 Fondazione IRCCS Istituto Nazionale dei Tumori, Prostate Cancer Program, Milan , Italy; 8 Mount Sinai School of Medicine, Department of Radiation Oncology, New York , USA; 9 Maastro clinic, Department of Radiation Oncology, Maastricht, Netherlands Antilles; 10 Universitätsmedizin Mannheim, Department of Radiation Oncology, Mannheim , Germany; 11 Independent Cancer Patients’ Voice (ICPV), ., London , United Kingdom; 12 Fondazione IRCCS Istituto Nazionale dei Tumori, Department of Radiation Oncology, Milan , Italy; 13 Fundacion Publica Galega Medicina Xenomica, Grupo de Medicina Xenómica (USC), Santiago de Compostela, Spain; 14 Ghent University Hospital, Department of Radiation Oncology, Ghent , Belgium; 15 University of Leicester, Department of Genetics and Genome Biology, Leicester , United Kingdom; 16 University Medical Center Hamburg-Eppendorf, Cancer Epidemiology Group, Hamburg , Germany

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